Inverted loss engineering in functional material covered waveguides

Optical waveguides, covered with thin films, which transmittance can be controlled by external action, are widely used in various applications from optical modulators to saturable absorbers. It is natural to suggest that the waveguide losses will be proportional to the covering material absorption. We demonstrate that under certain conditions this simple assumption fails. Instead, we observe the reduction of the film material absorption can lead to an increase in the waveguide propagation losses. For this, we use a side polished fiber covered with a single-walled carbon nanotube thin film whose absorption is attenuated either due to saturable absorption or electrochemical gating. For the films thicker than 50 nm, we observe saturable absorption to turn into light induced absorption with nonmonotonic dependence on the incident power. With a numerical simulation and analytical approach, we identify that this nontrivial behavior comes from mode reshaping and predict required parameters for its observation.Comment: 7 pages, 3 figure

Refractive indexes data

Refractive indexes of pure and nanotubes-doped samples of SiO2, TiO2 and ZrO

Data from: Holographic sol-gel monoliths: optical properties and application for humidity sensing

Sol–gel monoliths based on SiO2, TiO2 and ZrO2 with holographic colourful diffraction on their surfaces were obtained via a sol–gel synthesis and soft lithography combined method. The production was carried out without any additional equipment at near room temperature and atmospheric pressure. The accurately replicated wavy structure with nanoscale size of material particles yields holographic effect and its visibility strongly depends on refractive index (RI) of materials. Addition of multi-walled carbon nanotubes (MWCNTs) in systems increases their RI and lends absorbing properties due to extremely high light absorption constant. Further prospective and intriguing applications based on the most successful samples, MWCNTs-doped titania, were investigated as reversible optical humidity sensor. Owing to such property as reversible resuspension of TiO2 nanoparticles while interacting with water, it was proved that holographic xerogels can repeatedly act as humidity sensors. Materials which can be applied as humidity sensors in dependence on holographic response were discovered for the first time

Transparent Conducting Films Based on Carbon Nanotubes: Rational Design toward the Theoretical Limit

Funding Information: The authors thank Dr. D. Krasnikov and Dr. A. Goldt for fruitful discussions of the review and their valuable comments. D.A.I. and O.E.G. acknowledge the Russian Science Foundation (Project No. 21‐19‐00226). A.G.N. thanks the Council on grants of the President of RF. (grant No. НШ‐1330.2022.1.3). Publisher Copyright: © 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.Electrically conductive thin-film materials possessing high transparency are essential components for many optoelectronic devices. The advancement in the transparent conductor applications requires a replacement of indium tin oxide (ITO), one of the key materials in electronics. ITO and other transparent conductive metal oxides have several drawbacks, including poor flexibility, high refractive index and haze, limited chemical stability, and depleted raw material supply. Single-walled carbon nanotubes (SWCNTs) are a promising alternative for transparent conducting films (TCFs) because of their unique and excellent chemical and physical properties. Here, the latest achievements in the optoelectronic performance of TCFs based on SWCNTs are analyzed. Various approaches to evaluate the performance of transparent electrodes are briefly reviewed. A roadmap for further research and development of the transparent conductors using “rational design,” which breaks the deadlock for obtaining the TCFs with a performance close to the theoretical limit, is also described.Peer reviewe

High Performance Hydrogen Evolution Reaction Catalyst Based on Single-Walled Carbon Nanotubes Decorated by RuOx Nanoparticles

| openaire: EC/H2020/722614/EU//ELCORELWe report a cathode material based on plasma-treated single-walled carbon nanotubes decorated by RuOx nanoparticles using atomic layer deposition. We have examined cathode performance towards hydrogen evolution reaction by tailoring material wettability, conductivity yielded by plasma treatment, and the catalyst loading. We discuss that nucleation of particles is facilitated by the appearance of carboxylic and hydroxyl groups triggered by oxygen plasma action. The best performance is associated with samples containing RuOx particles of 4–5 nm, which show hydrogen evolution onset potential to be about −5 mV (vs. RHE) in 0.5 M H2SO4 measured at a current density of −1 mA cm−2 and Tafel slope of 47.5 mV/dec. The material possesses stable performance at −10 mA cm−2 with a potential of about −160 mV.Peer reviewe

Optimization of Optoelectronic Properties of Patterned Single-Walled Carbon Nanotube Films

We propose a novel strategy to enhance optoelectrical properties of single-walled carbon nanotube (SWCNT) films for transparent electrode applications by film patterning. First, we theoretically considered the effect of the conducting pattern geometry on the film quality factor and then experimentally examined the calculated structures. We extend these results to show that the best characteristics of patterned SWCNT films can be achieved using the combination of initial film properties: low transmittance and high conductivity. The proposed strategy allows the patterned layers of SWCNTs to outperform the widely used indium-tin-oxide electrodes on both flexible and rigid substrates.Peer reviewe